This invention relates to a tool useful in removing a tight-fitting lid from a vessel, and is more particularly concerned with a tool useful in removing the upper lid from a pressure cooker.
Pressure cookers or autoclaves are in widespread home use for the cooking or sterilization of foodstuffs, and are widely used in industrial applications for heat treatment and sterilization of various materials. In general, pressure cookers or autoclaves are comprised of a sturdy heat-conductive cylindrical vessel and a removable circular lid having a rim capable of making an airtight seal with the vessel. The lid engages the vessel by bayonet-type fittings whereby seating and removal of the lid is accomplished by rotational movement in a plane perpendicular to the cylindrical axis of the vessel. To assist in such rotational movements, a handle is provided in the lid. A matching alignment handle is provided in the vessel adjacent its open upper extremity at a site corresponding to the locking point of the lid. The handles of the lid and vessel serve not only to facilitate turning, but indicate proper alignment and enable the pressure cooker to be comfortably lifted.
When the vessel, containing a volatile liquid such as water, is sealed with its lid and subjected to heating, the liquid develops an autogenous pressure, the magnitude of which is dependent upon the temperature and the vapor pressure of the liquid. A safety valve in the lid permits venting of vapors to avoid excessively high pressures.
The pressure cooker is capable of subjecting a foodstuff to controlled and uniform elevated temperatures without causing drying or oxidation, and for these reasons is eminently suited for the cooking of foods. In sterilization applications, the combined effects of high temperature and high water vapor pressure kill microbes without adversely affecting foodstuffs intended for preservation by canning or bottling. At the termination of a process utilizing a pressure cooker, the lid must be removed to gain access to the interior of the vessel. Even when pressure is vented so that no pressure gradient exists between the interior and exterior of the pressure cooker, the lid, because of its tight-fitting nature, may be difficult to rotate to effect its removal. Because of the round configuration of the pressure cooker, it is difficult to grasp the vessel and lid in a manner to try to exert a separating force. The use of hammers or other percussive devices to effect separation may cause damage to the handles or other parts of the pressure cooker.
It is accordingly an object of the present invention to provide a tool for separating the lid from the vessel of a pressure cooker.
It is a further object of this invention to provide a tool of the aforesaid nature which will not damage the pressure cooker.
It is a still further object of the present invention to provide an improved tool as in the foregoing object of simple and rugged construction which may be economically manufactured.
These objects and other objects and advantages of the invention will be apparent from the following description.